[Dovecot] mdbox

Reviewing some mailing list archives and the wiki, I still don't have a real clear picture of why I'd want to use mdbox. What I've taken from the info I've reviewed says mdbox is more complicated (than sdbox), has greater potential for breakage (simply because it's more complex), and has a theoretical performance impact depending on the exact filesystem/hardware used.

Was that an accurate summary? Is mdbox something that was desired to solve a particular problem?

Daniel